What should I use to prevent my boat from taking on water? And is it necessary to use marine grade plywood?

No you do NOT have to use "marine grade" plywood. In fact, you will have a very hard time finding it anymore. That is an old truth, that is no longer true. Today, AA or AB EXTERIOR GRADE plywood is better then "marine grade' plywood was in the 40s, 50s, 60s, & 70s (the peak of wood boat building days).

I actually built boats for over 40 years, and I always get heat over the "marine plywood" thing - but for sure, only those that have never built boats, don't know plywood, and have only read the 'dated' books - disagree anymore. Fact is, plywood, like the steel used to build the Titanic - is much-much better today then it used to be.

Here is a great link for boat building methods: (what you need, the "stitch & glue" method seems best & easiest:

http://www.glen-l.com/boatbuilding-methods/

How do you water proof your wood and your vessel?

You MUST glue all your joints with and laminate (encapsulate) it with boat epoxy. This means both sides, inside and out and all cut corners and edges,

You could also apply a layer of fiberglass - it is actually much easier then you think, and cheaper then you think. . .

Here is a link to buy epoxy:

http://www.uscomposites.com/epoxy.html

Anyone that tells you "marine grade" plywood would be less costly since both sides of vessel do not have to be coated" doesn't have any experience or understanding of what marine grade plywood is.

Marine Grade (like any other) MUST be protected inside & out from the elements as does all wood. If you DO NOT laminate or protect your plywood inside and out - your boat won't last a year. A thin coating of boat epoxy will protect & prevent your wood from rot, worms, and disease.

I suggest you visit http://www.glen-l.com/ and read/learn all you can. It would probably be a great idea to check out (and buy) a set of boat building plans from them. They come with complete instructions and a BOM, and they are simply great plans for first time builders.

Marine plywood had been around for 40 years. Most plywood these days has water resistant glue, so the only difference now is the "voids". In normal practice there are voids that are under the outer sheets of plywood. The better the grade of plywood the fewer voids. Marine plywood should have none. Clearly many boat manufacturers use something other than marine grade plywood. There are some specifications as to density of the wood and also strength, but it takes a very knowledgeable plywood man to really know the specifications.

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you dont mention where you're getting your plans from. If drawing your own I advise spending a LOT of time checking what others have done. For a small boat the cost of the plans is only a small part of the total cost (usually less than the paint)

You dont have to use marine ply but you do have to use good ply. Most good ply these days uses the same adhesives as marine ply - only the quality of the plys themselves differ..

You can always do a boil test on any cheaper ply you want to use.

This is a boat that wont be living on the water by the sound of it.

It may sound silly but (pushing my own barrow) take a look at the Duckchaser design - a number of them are used for fishing, noone has mounted a trolling motor yet that I know of but it wouldn't be difficult , though I'd upsize to the Goosechaser (same design but 6" more canvas in the centre) to increase the payload to 360 lb but still gives a boat that folds up & can be carried one handed.

So..

If you want to build your own boat here: http://boatplans.toptips.org/

you'll find a comprehensive collection of 518 boat plans, 40 videos and about 500 pages of boat building guides. I've just bought the entire package. The product offers step by step blueprints on over 518 boats and video lessons on boat building. The creator, Martin Reid offers a simple, efficient and user-friendly system to construct any type of boats in a simple way. This site shows the user how to build over 500 different types of boats ranging from simple canoes and kayaks to complex designs like a cabin cruiser.

Regards

Cameron, believe using "marine grade" plywood would be less costly since both sides of vessel do not have to be coated to avoid de lamination. However, make your own "educated decision" after exchanging views with those that have and are building boats. Go to Glenn L website and you'll find pictures of "completed and work in progress boats". Moreover, you'll be able to communicate with them and get "first hand" opinions regarding your project.

Download 500 Boat Plans Here : http://boatplans.naturallygo.com/?XlD

use marine grade plywood or oak

ask about the newer epoxy sealers and paint.

unless you seal the ply well, maybe with glass-fibre sheathing, marine quality is preferable but very expensive. use ordinary, exterior standard ply, paint it well, and store up-side down